A classical theorem of Hurwitz says that if $R=\mathcal{O}_K$ is the ring of integers of a number field, then the group $SL_2(R)$ is finitely generated.
Unfortunately, the original paper of Hurwitz is written in German, that I cannot read/understand.
My question is: is there is somewhere a modern exposition of a proof of this result?
Remark. I am aware of the works of Varsentein, Bass, Serre ,Swan,Cohn ...on $SK_1(R)$ and the connections with the possible generation of $SL_2(R)$ by elementary matrices. However, Hurwitz work was prior to all of that,and I would like to have a proof free from $K$-theoretic considerations , in the spirit of Hurwitz's original proof.
